1. Field of the Invention
The present invention relates in general to a sliding type coupling device and a method of producing the same, and more particularly to such a sliding type coupling device which is simple in construction and is substantially free from rattling and variation of its sliding torque, and a method of producing such a coupling device.
2. Discussion of the Related Art
There are known sliding type coupling devices of one type as disclosed in Publication No. 55-39853 of examined Japanese Utility Model Application and Publication No. 55-124314 of unexamined Japanese Utility Model Application. The coupling device of this type includes: an inner member provided with a sliding contact portion having a spherical or cylindrical outer circumferential surface; a cylindrical or sleeve-like outer member which is open at at least one axial end and receives therein the sliding contact portion of the inner member; and a slidable member made of a synthetic resin and attached to an inner surface of the outer member. The sliding contact portion of the inner member is slidably supported by the inner circumferential surface of the slidable member.
In the known sliding type coupling device as described above, the slidable member is attached to the outer member in the manner as disclosed in the above-identified publications. More specifically, the slidable member is first inserted into the outer member, and is kept in position with its opposite axial end faces held or retained by retainer rings that are press-fitted into inner circumferential surfaces of open end portions of the outer member. The retainer rings serve to prevent the slidable member from slipping out of the outer member. In order to assure higher resistance to slipping of the slidable member out of the outer member, and improved capability of the coupling device to endure axial loads, circumferential grooves may be preferably formed in the inner surfaces of the open end portions of the outer sleeve, so as to receive or engage with the retainer rings for holding the slidable member in position.
With the slidable member attached to the outer member in the manner as described above, however, rattling may occur between the slidable member and the outer member, due to loose engagement of the retainer rings with relevant portions of the outer member, dimensional errors in the slidable member and outer member, and other factors. Further, the axial gripping force applied by the retainer rings to the slidable member may not be stabilized, causing variation of the pressure at sliding surfaces of the inner member and slidable member, whereby the sliding capability may vary from one product to another.
To assure tight engagement of the retainer rings with the outer member, it is proposed to caulk an outer peripheral portion of the retainer ring against the outer member, so that the ring is fixedly fitted in the annular groove formed in the outer member, as disclosed in JP-A-64-6512. However, the thus constructed coupling device must be manufactured with low efficiency, at an increased cost, due to a need for an exclusive process step for caulking the retainer ring. Further, the coupling device still suffers from rattling of the slidable member and variation of the sliding capability, due to dimensional errors of the slidable member and outer member, for example, even if the retainer ring is fixed by caulking to the outer member.